The initiators are not being displayed in the igroup screen because there might be an issue with the zoning on the switches or the server might not be powered up. Zoning is essential as it defines communication access between initiators and targets in a SAN, and if done incorrectly, can prevent initiators from appearing. Additionally, if the server is not powered up, its HBAs (Host Bus Adapters) will not be online, thus their WWPNs (World Wide Port Names) won't be detected or displayed.